GB1600873A - Dental filling material - Google Patents

Description

PATENT SPECIFICATION ( 1 ") 1 600 873

C ( 21) Application No 20125/78 ( 22) Filed 17 May 1978 1 ( 31) Convention Application No 2728764 ( 32) Filed 25 June 1977 in O ( 33) Federal Republic of Germany (DE) O ( 44) Complete Specification published 21 Oct 1981 ( 51) INT CL 3 C 08 L 33/04 A 61 C 5/00 C 08 J 5/00 C 08 K 3/22 ( 52) Index at acceptance C 3 P KA C 3 W 225 301 305 C 3 Y B 120 B 123 ( 72) Inventors ROBERT SCHMITZ-JOSTEN MICHAEL WALKOWIAK MANFRED BORGARDT BERNHARD LEUSNER HANS-HERMANN SCHULZ and CARLHANS SULING ( 54) DENTAL FILLING MATERIAL ( 71) We, BAYER AKTIENGESELLSCHAFT, a body corporate organised under the laws of the Federal Republic of Germany, of Leverkusen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 5

The present invention relates to formulated dental filling materials, based on organic plastics material containing inorganic filler, suitable for use in paste/paste systems.

Dental filling compositions based on organic plastics material filled with inorganic filler are known from U S Patent 3,066,122 In contrast to conventional 10 organic plastics material provided with inorganic filler, the organic plastics material containing filler for use in dentistry must satisfy certain processing criteria which are practicable and customary in dental practice In addition, the mechanical properties of the hardened filling material products should remain substantially unchanged for years, even in the oral environment, and the products 15 must be highly compatible both with the mucous membrane of the mouth and with the dental tissue.

An example of a suitable organic filler according to U S Patent 3,066,112 is silanised quartz glass, to which flint-glass powder can be added as a filler component in order to achieve X-ray opacity, Bis-GMA mixed with a reactive 20 diluent is used as the organic "binder".

The disadvantage of dental filling compositions of this type is that they are used in a powder/liquid system, which is difficult and inconvenient to handle The proportion of filler to organic binder is not automatically constant in this kind of application form: thus not only are different mechanical properties obtained in 25 individual fillings from one case to the next and are seldom optimum, but also the polymerisation shrinkage during the hardening of the filling is not automatically set at the low level required clinically.

It is also known to use dental filling compositions, based on organic plastic material containing inorganic filler, for application in paste/paste systems Thus, 30 US P 3,926 906 and DT-AS (German Published Specification) 1,929,831 describes how systems of this type, which produce clinically useful fillings, can be built up In this case it is an essential characteristic of such paste/paste systems that the "catalyst paste" and the "activator paste" should have substantially the same composition from the point of view of the chemical composition of the 35 components, with the proviso that constituents of the pastes which are only present in small amounts, such as, for example, different dye-stuff additives or catalvst/activator components which differ chemically, should be distributed evenly throughout the pastes.

This system indeed has on the one hand the advantage that the mixing process 40 can be carried out particularly easily, but on the other hand it has the disadvantage that a graded X-ray opacity, such as is desirable in many cases for dental filling 2 1,600,873 compositions and frequently is also necessary, cannot be obtained since the filling has a constant X-ray absorption, independently of the mixing ratio, because the pastes are built up chemically in the same manner It is therefore not possible to adjust the intensity of the X-ray opacity by varying the mixing ratio of the activator paste and catalyst paste 5 However, a graded X-ray opacity is desirable, depending on the extent and volume of the dental fillings If, for example, a tooth is built up extensively by dental filling materials based on organic plastics material containing inorganic filler, a relatively low X-ray opacity is desired so that the extent of the hard tooth tissue substance or of the composite structure can be readily ascertained on an X 10 ray photograph during later prosthetic work, for example the fitting of a crown On the other hand, fillings of relatively low volume, such as, for example, fillings in the neck of the tooth, require a higher X-ray opacity so that the filling can be readily identified.

A further disadvantage of paste/paste systems in which the pastes are identical 15 from the point of view of the main chemical composition of the components and the proportions of the components is that the catalyst pastes always have a limited and varying shelf life if these pastes contain a filler which causes a relatively high absorption of X-ray radiation because of a relatively high content of elements with high atomic numbers Even in low amounts, however, the ions of elements with 20 relatively high atomic numbers can cause catalytic decomposition of peroxides.

The present invention provides formulated dental filling material (as hereinafter defined) comprising a polymerisable organic plastics material containing inorganic fillers, which filling material comprises at least two pastes, each being solvent-free and comprising a monomer, capable of forming an intimate 25 admixture with one another in a paste/paste system in which hardening is initiated by means of a peroxidic initiator and an accelerator, wherein said at least two pastes contain different inorganic fillers with different chemical constitutions such that one of said at least two pastes contains filler with a higher proportion of elements with an atomic number of 26 or greater than does the other of said at least 30 two pastes, and wherein said other of said at least two pastes contains the peroxidic initiator and the said one paste contains an accelerator.

It is surprising that the pastes according to the invention, in which the fillers used in the individual pastes differ substantially in their chemical composition, can be processed without additional measures so as to produce homogeneous dental 35 fillings in the same way as pastes which are essentially built up from chemically identical fillers and which indeed have a good tolerance towards the substrate alone, but do not enable the X-ray opacity to be adjusted to the clinically desired value by way of the mixing process.

Formulated dental filling materials based on organic plastics material 40 containing inorganic filler are understood as compositions which are ready for use, that is to say which have all the useful characteristic parameters necessary for adjusting the clinically relevant properties to the required properties, all the useful characteristic parameters necessary for adjusting the aesthetic characteristics as desired and all the useful characteristic parameters required for their application 45 Suitable materials include, in particular, those organic plastics materials which are formed from low-molecular monomers by vinyl polymerisation or optionally by polyisocyanate polyaddition, with hardening, and in which a substantial proportion of the whole hardened composition consists of inorganic fillers The organic chemical component of the pastes which can be hardened, is also called a 50 "binder".

Clinically relevant properties are firstly the required mechanical strength, and furthermore adequate stability in the oral cavity environment, a sufficient X-ray opacity and good inertness towards dental tissue and surrounding mucous membranes 55 Desired aesthetic characteristics are to be understood herein as, inter alia, the properties which enable the colour and surface structure to be matched as well as possible to that of the teeth to be filled The colour adjustment may be effected firstly by adding dyestuffs in small amounts; secondly, however, the required colour can also be imparted by using materials of greater or less transparency 60 which after hardening together ensure that, as a result of their partial transparency.

the colour of the filling gives the appearance of being matched with the original colour of the tooth.

Useful characteristic parameters required for the application of the material are understood herein as the characteristic parameters such as the processing time 65 hardening time, mixing time and consistency of the pastes and of the paste/paste mixtures.

The known isocyanates and the compounds which are active in a Zerewitinoff reaction and are suitable for polyisocyanate polyaddition, such as primary and second amines, hydrazine derivatives and/or polyalcohols, are suitable for use in a 5 hardening procedure involving a polyisocyanate polyaddition.

Monomers which can be hardened by vinyl polymerisation are compounds which contain at least one polymerisable carbon double bond Those monomers which are polyfunctional with respect to the double bonds, that is to say which lead to highly crosslinked polymers or copolymers, are particularly suitable for building 10 up the organic plastics material according to the invention.

Examples of suitable monomers are methacrylic acid esters or acrylic acid esters of aliphatic or aromatic polyols, for example ethylene glycol dimethacrylate, diethylene glycol dimethacrylate or triethylene glycol dimethacrylate or the corresponding acrylic acid esters, and also compounds such as trimethylolpropane 15 trimethacrylate, triacrylylformal, or the methacrylic acid esters of bisphenol A or derivatives thereof, such as, for example, Bis-GMA, or the bis (methacrylic acid ester) of the bis ( 2 hydroxyethyl ether) of bis-phenol A Examples of further monomers which are suitable for building up the dental filling compositions according to the invention are those which are known from U S Patent 3, 179,623, 20 U.S Patent 3,730,947 or from DT-OS (German Published Specification), 2, 419,887.

The formulae of examples of suitable comonomers are listed in the following summary in which the symbols have the following meanings:-

R = CH 2 = C CO CH 2 = CH CO CH 3 R= H -CH 2 OR 25 n= 1 -4 m= 0-4 RO-CH 2-CH-CH 3 2, 2 OH OH RO-CH 2-CH-CH 2-0 3 +G) O-CH 2-CH-CH 2-OR OR OR RO-CH 2-CH-CH 2-0 O-()+{>-O-CH 2-CH-CH 2-OR 30 0-CO-NH (Ii) O-CO-NHR-O-CH 2-CH 2-O-CH 2-CH-CH 2 -O (+I"O'-O-CH 2-CH-CH 2-O-CH 2-CH -O-R R H<< 2 ()@FH<< -l{ +<) 2,< 35 O OH OH OH RO (CH 2)n O X D O( 2 n R RO (CH 2)n-O-()-S Oj 2 i -o (CH 2)JOR CH OH OH 1.600873 1.600,873 O-C 52-,o-%,-CH 2-o -C 27 CH CH -CII CI-ICH O-Q/-0,-:H CH OR C C ' CH CH HO "OR RO-C 22 O-a-I 2, 2 9-CH 2-'CH 2-OR CH BO-(CH 2)n-O 4-<-G-} (CH 2)n-OR RO-2 c Hi C-2 i C-2-i CH 2-4 D-C-IH-OR E COH RO,/CH 2-00 C(CH 2) 4-C O H 2OH HO OR H/-CH 2-OR HO H, 3 RO,C-2- OR HO C OR OR "-&(D-O-R RO-&G -OR l{>q'2 q H 2-O- HOH -H 2-CH 2-C O CH 2-CH 2-OR GOHH 2 -CHH 2 C 2 HO O-CO 2 2 -< 2 "H-CH H 2-CI-H 2 \ -R HO P H-27 + G -CH 2-OR CH-D H 2 O CH 3 CH'3 KLFC 2 OK -CH 2-OR M-C 2-K -O 5 Rih R CX:H 2-CH 2 'OR 2 COOM -CH 2-OR in the ortho-, meta or para-form A compound of the general formula:

R (O-D-O-X), OD-OR, wherein HO-D-OH is a polyol and 10 HO-X-OH is a dicarboxylic acid, and in particular a saturated or unsaturated, cyclic or acyclic polyol and dicarboxylic acid.

RO-CH 2-CH 2-O-CO-NH -l NH-CO-O-CH 2-CH 2-OR CH 3 ?H 3 CH 3,C 3 RO-CH 2-C-OCONH-CH 2-C-CH 2-CH-CH 2-CH 2-NH-CO-O-C-CH OR 2, 2, 2 2, 2 CH 3 CH 3 CH 3 R-O-CH 2-CH 2-O-CO-NH CH 3 -O-CH 15 D NH-CO-O3 (average molecular weight 2,500) RO-C 3 H 6-OCO-NH-o CH 3 CH 3 "-NH-COO-C 3 H 6-OR NH NH C= O _( 3 H 1,600,873 R C 2-<>C 2) -OCH 2 -CH-CH 2 -OR 0 _ o NH NH-/ and prepolymers containing NCO and urethane groups, reacted with hydroxyalkyl methacrylate according to DT-OS (German Published Specification) 2,419, 887 or

French Patent Specification 2,271,807.

In many cases it is particularly advantageous to use a mixture of different 5 monomers as the binder for mixing with the inorganic filler for the preparation of the pastes Mixing enables, for example, on the one hand with refractive index of the resulting plastic to be matched with that of the organic fillers and sufficient transparency of the finished fillings thus ensured, and on the other hand pastes having the desired viscosity and consistency may be prepared relatively easily using 10 mixtures of different organic monomers A preferred embodiment of the dental filling material according to the invention contains a mixture of polymerisable derivatives of bis-phenol A and dimethacrylates of aliphatic glycols, such as, for example, ethylene glycol, butane-l,4-diol, hexane-l,6-diol, diethylene glycol or triethylene glycol, as the binder As already mentioned it is preferred to initiate the 15 curing of the dental filling compositions by an activating system consisting of a suitable peroxidic catalyst such as benzoyl peroxide and an activator such as N,Ndimethylparatoluidine and paratoluenesulfinic acid Other suitable activators are described, for example, in the US Patents No 2,558,139, 3,541,068, 3,926, 906 and 3,359,533 By mixing the catalyst containing past with the activator containing past 20 radicals are generated which start the polymerisation of the monomers called binders.

Suitable inorganic fillers for the dental filling material according to the invention are on the one hand products such as rock crystal, quartzite, cristobalite or A 1203, which contain no elements with atomic numbers of 26 or greater which 25 may catalyse degradation of peroxides, such as, for example, Cu, Fe, Pb, Bi, Sn and Zn, and which also contain, for example, only traces of less than 2 0 % of the elements Ba or La On the other hand, however, fillers in the form of glasses or glass ceramics, which contain a high proportion of elements which absorb X-rays well or scatter them considerably, are suitable for use as a filler for the paste 30 containing no peroxidic catalyst The use of glasses containing, for example, Ba as a component of inorganic fillers is described in detail, for example, in U S Patent 3,808,170, with the proviso in that case that both the peroxidic catalyst paste and the activator paste contain this filler in equal amounts Further inorganic fillers which are suitable agents for absorbing X-rays are described, for example, in DT 35 OS (German Published Specification) 2,347,591 The glass ceramics described in this application contain La and Zr as elements which cause relatively intensive absorption of the X-ray radiation.

These glass ceramics are furthermore distinguished by a particularly favourable coefficient of thermal expansion 40 The filler may be processed by a grinding operation so as to produce a fineparticled powder, and the average particle size should be from I to 150 micron In some cases addition of glass beads with a particle size < 40,u (for example "Reflexperlen" (Trade Mark) RPG 22 from Jenaer Glaswerke Schott u Gen.

(Western Germany) give the pastes a good processability, it has to be treated with a 45 organosilane keying agent Addition of highly dispersed submicron silica in amounts of about 2 %, relative to the amount of total filler, are suitable in some cases for keeping the consistency of the paste constant over a relatively long period because settling of the coarser filler is delayed by highly disperse additives of this type 50 The preparation of the pastes by mixing the binders and the fillers can be carried out in the laboratory on glass or porcelain plates or in glass or porcelain containers The pastes are prepared on an industrial scale using automatically operated mixing units, of which the following may be mentioned as examples: JEL 25/53 mulling machine from Messrs Engelmann, Ludwigshafen; RMO type mortar 55 mill from Messrs Retsch KG, Haan; a high-speed micro-mill from Messrs Retsch KG, Haan; ball mill from Staatliche Porzellan-Manufaktur Berlin; "Pulverisette 5 " 1,600,873 planetary ball mill from Messrs A Fritsch, Idar-Oberstien; planetary mixer from Messrs Drais, Mannheim; planetary mixer from Messrs Spangenberg, Mannheim:

kneader from Messrs Werner and Pfleiderer, Stuttgart; kneader from Messrs.

Meili, Zurich; mixer from Messrs L 6 dige, Paderborn; and mixer from Messrs.

AMK, Aachen 5 Roll mills, such as, for example, the "Exakt 50 " triple roll mill from Messrs O Herrmann, Horderstedt, can also be advantageously used for the final homogenisation.

The proportions of filler to binder in the pastes are limited on the one hand by the desired consistency; it must be easy to introduce the pastes into cavities and 10 this means that too high a content of inorganic fillers is precluded On the other hand, a high hardness is required of the hardened filling and in addition the shrinkage caused by the hardening should be as low as possible Both requirements are best fulfilled when the proportion of filler is as high as possible In general, pastes which contain from 55 to 85 %, preferably from 60 to 80 %, of filler are used 15 Example 1

22.19 parts by weight of a mixture of 64 % bisphenol A diglycidyl dimethacrylate and 36 % triethylene glycol dimethacrylate, containing as an amine activator 1,2 % N,N di ( 2 hydroxylethyl) p toluidine, are initially introduced into a "Pulverisette 5 " planetary ball mill (Messrs Alfred Fritsch) The 20 ball mill is provided with agate cups and agate balls 9 59 parts by weight of finely ground a-quartz (rock crystal), which has been treated with 0 4 % of y methacryloxypropyl trimethoxysilane, relative to the quartz, are added to the mixture 66 74 parts by weight of barium-containing glass powder "Schott" (Trade Mark) 8235 (Messrs Jenaer Glaswerke Schott und Gen), which has also been 25 treated with 0 4 % of the same silane, relative to the glass, are also added 1 48 parts by weight of highly disperse silica "HDK 15 P" (Trade Mark-Messrs Wacker Chemie) are added in order to adjust the consistency of the paste The colour of the composite paste is adjusted by adding 10 ppm of Irgazingelb 3 RLT, 16 ppm of Helioechtgelb ER, 2 2 ppm of Makrolexrot G and 0 3 ppm of Makrolexrot 5 B A 30 kneadable composite paste which is designated Paste A is obtained in the planetary ball mill within a mixing time of 20 minutes.

20.18 parts by weight of the same mixture of bisphenol A diglycidyl dimethacrylate and triethylene glycol dimethacrylate, to which 2 % of benzoyl peroxide has been added, are initially produced into a separate agate cup in the 35 planetary ball mill, to make a paste activated with benzoyl peroxide (Paste B).

78.47 parts by weight of finely ground a-quartz (rock crystal), which has been silanised with 0 4 % of y methacryloxypropyltrimethoxysilane, relative to the quartz, are added to the mixture 1 35 parts by weight of highly disperse silica HDK 15 P are also added A kneadable composite paste (Paste B) results after a 40 mixing time of 20 minutes.

Paste A and Paste B are mixed with one another in a weight ratio of 1:1.

Cylindrical test pieces with a diameter of 6 mm and a height of 12 mm are prepared from the mixture in accordance with FDI Specification No 5 and have, after storing in water at 37 C for 24 hours, a compressive strength of 210 N/mm 2 45 Test pieces consisting of the same mixture and having the dimensions 25 mmx 2 mmx 2 mm, which are prepared in accordance with DIN draft specification

00 13 921, have, after storage in distilled water at 37 C for 24 hours, a flexural strength of 82 N/mm 2.

Comparative Storage Experiments on Composite Pastes Containing Benzoyl Peroxide 3 g of benzoyl peroxide and 0 2 g of 2,6 di t butyl 4 methylphenol are dissolved in a mixture of 64 g of bisphenol A diglycidyl methacrylate and 36 g of triethylene glycol dimethacrylate at room temperature This solution is then mixed, in the percentage indicated, with the X ray opaque silanised fillers indicated in 55 the Table which follows and the mixture is weighed into polyethylene containers and stored in a drying cabinet at 40 C.

The peroxide content is determined at time intervals of about I week and is calculated as a percentage of the initial value of 100.

The filler-free peroxide solution and a paste prepared with silanised rock 60 crystal powder are included in the test as a control.

1,600,873 TABLE

Decrease in the Peroxide Content on Storage at 40 C Solution without filler Paste containing 78 3 o of silanised rock crystal Paste containing 73 2 % of Ba-glass "Schott"T' 8235 Paste containing 75 % of La-glass "Schott P" 1816 (prepared according to DT-OS (German Published Specification)

2,347,591) Paste containing 81 o of Ba-glass from Messrs Kimble+++' 0 5 12 % 94 9,% O 93 6 % 0 5 12 % 96 7 % 94 5 % 0 7 14 % 91 6 % 806 +)o/ 0 7 14 % 53 7 +X% 42 2 +'% 0 7 14 /0 66 1 1 % 31 1 +}% 19 26 33 40 47 Days 92.1 % 88 4 % 87 1 %, 84 8 % 83 85 " benzoyl peroxide 19 26 33 40 47 61 Days 90.0 % 88 1 % 82 00 % 81 7 % 81 7 %, 82 0 % benzoyl peroxide 23 Days 85.8 +)% benzoyl peroxide 23 Days 37.0 +}% benzoyl peroxide 23 Days 18.5 +,/o benzoyl peroxide "Ray Sorb" T 3000 (Trade Mark) +) partially polymerised +') Messrs Schott Gen, Mainz, Western Germany tt) Messrs Kimble O-I, Toledo, Ohio, U S A (Division of Owens-Illinois, U.S A) OC be j 9 1,600,8739

Claims (1)

1. WHAT WE CLAIM IS:-

   1 A formulated dental filling material (as hereinbefore defined) comprising a polymerisable organic plastics material containing inorganic fillers which filling material comprises at least two pastes, each being solvent-free and comprising a monomer, capable of forming an intimate admixture with one another in a 5 paste/paste system in which hardening is initiated by means of a peroxide initiator and an accelerator wherein said at least two pastes contain different inorganic fillers with different chemical constitutions such that one of said at least two pastes contains fillers with a higher proportion of elements with an atomic number of 26 or greater than does the other of said at least two pastes, and wherein said other of 10 said at least two pastes contains the peroxidic initiator and the said one paste contains an accelerator.

   2 Formulated dental filling material as claimed in Claim 1 in which the polymerisable organic plastics material is one which hardens by means of vinyl polymerisation with or without polyisocyanate polyaddition 15 3 Formulated dental filling material as claimed in Claim 1, or Claim 2 which contains a mixture of polymerisable derivatives of bisphenol A and dimethacrylates of aliphatic glycols as binder.

   4 Formulated dental filling material as claimed in any one of Claims I to 3 wherein each of the pastes contains from 55 to 85 %, by weight of filler 20 Formulated dental filling material as claimed in Claim 4 wherein each of the pastes contain from 60 to 80 % by weight of filler.

   6 Formulated dental filling material according to any one of Claims I to 6 in which the peroxidic initiator is benzoyl peroxide.

   7 Formulated dental filling material according to any one of Claims I to 7 in 25 which the filler in said other of the at least two pastes comprises at least one of rock crystal, quartzite, cristobalite or A 1203.

   8 Formulated dental filling material substantially as described hereinbefore with particular reference to the Example.

   9 A dental filling material pack in which said material comprises a 30 polymerisable organic plastics material containing inorganic filler, said pack comprising at 'least two pastes, each being solvent-free and comprising a monomer, usable together in a paste/paste system, in which hardening is initiated by means of a peroxidic initiator and an accelerator, for forming dental fillings, wherein one of said at least two pastes contains inorganic filler with a higher proportion of 35 elements with an atomic number of 26 or greater than does the other of said at least two pastes, and in which said other of said at least two pastes contains the peroxidic initiator, and the said one paste contains an accelerator.

   A method of producing a formulated dental filling material comprising admixture of at least two pastes as defined in any one of the preceding claims 40 11 A formulated dental filling material according to any one of Claims I to 8 for use in filling cavities in teeth.

   12 A dental filling material pack according to Claim 9 for use in filling cavities in teeth.

   For the Applicants, CARPMAELS & RANSFORD, Chartered Patent Agents, 43, Bloomsbury Square, London, WCIA 2 RA.

   Printed for Her Majesty's Stationery Office, by the Courier Press, Leamington Spa, 1981 Published by The Patent Office 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.

   1,600,873